Stroke is the third most common cause of death in the United States and the most disabling neurologic disorder. Approximately 700,000 patients suffer from stroke annually. Stroke is a syndrome characterized by the acute onset of a neurological deficit that persists for at least 24 hours, reflecting focal involvement of the central nervous system, and is the result of a disturbance of the cerebral circulation. When a patient presents with neurological symptoms and signs which resolve completely within 1 hour, the term transient ischemic attack (TIA) is used. Etiologically, TIA and stroke share the same pathophysiologic mechanisms and thus represent a continuum based on persistence of symptoms and extent of ischemic insult.
Outcome following stroke is influenced by a number of factors, the most important being the nature and severity of the resulting neurologic deficit. Overall, less than 80% of patients with stroke survive for at least 1 month, and approximately 35% have been cited for the 10-year survival rates. Of patients who survive the acute period, up to 75% regain independent function, while approximately 15% require institutional care.
The majority of the strokes are caused by occluded vessels that deprive the brain of oxygen-carrying blood. The vertebral and basilar arteries typically provide blood supply to the brainstem, the cerebellum, and the posterior cerebrum. Infarction in these areas of the brain can produce dire consequences. For example, basis pontis infarction due to basilar artery occlusion may lead to a “locked-in state” characterized by quadriplegia and paralysis of the bulbar muscle such that the patient can only communicate by moving eyes or eyelids. Dysfunction of the reticular activating system, which controls autonomic function of vital body organs, e.g., the cardiac and respiratory function, may lead to coma or death. Ischemia caused by vertebrobasilar insufficiency often produces multifocal lesions including a considerable longitudinal extent of the brain stem, thereby giving rise to a combination of symptoms, including dizziness, double vision, facial weakness, and gait instability.
Current treatments for patients with ischemia or infarction in the territory of the vertebral or the basilar artery include anticoagulation, e.g., heparin, and supportive care. Recently, vertebral thromboatherectomy, percutaneous angioplasty, and stenting are increasingly performed to remove the occluding lesions. However, the main complication of these procedures is distal embolization of atheromatous material downstream of the vertebral artery being treated, causing stroke in the posterior circulation.
New devices and methods are thus needed in patients undergoing invasive procedures for definitive or prophylactic treatment of occluding lesions in the vertebrobasilar circulation, thereby minimizing the risk of distal embolization to prevent ischemic stroke.